C70 Overvoltage Faults

I'm having electrical issues with my 2000 Volvo C70, gasoline engine. It's got about 85k kilometers on it. I keep getting fault memory entries related to overvoltage, and it's causing systems to fail, weak battery when starting, just a general electrical malfunction. I'm not sure where to even start looking. Any ideas?

4 comment(s)

Overvoltage huh? Have you checked the battery itself? A heavily discharged or defective battery can sometimes cause these symptoms. How old is it?

The battery is about two years old, so not ancient, but also not brand new. How would a bad battery cause overvoltage, though? I thought it would be the opposite!

A failing battery can cause the charging system to overcompensate, leading to an overvoltage situation. While other components could cause overvoltage, a weak battery is a likely candidate and is also consistent with your starting issues. Either way, those symptoms point to an electrical issue. I'd suggest getting it properly diagnosed by a workshop.

Thanks for the tip! I took it to a shop, and you were right – it was a defective battery causing the alternator to work overtime. New battery and everything's running smoothly again. Cost me 290€ Appreciate the help!

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